/**
 * Default configs.
 */
var DEFAULT_DELIMITER = '/'
var DEFAULT_DELIMITERS = './'

/**
 * The main path matching regexp utility.
 *
 * @type {RegExp}
 */
var PATH_REGEXP = new RegExp([
    // Match escaped characters that would otherwise appear in future matches.
    // This allows the user to escape special characters that won't transform.
    '(\\\\.)',
    // Match Express-style parameters and un-named parameters with a prefix
    // and optional suffixes. Matches appear as:
    //
    // ":test(\\d+)?" => ["test", "\d+", undefined, "?"]
    // "(\\d+)"  => [undefined, undefined, "\d+", undefined]
    '(?:\\:(\\w+)(?:\\(((?:\\\\.|[^\\\\()])+)\\))?|\\(((?:\\\\.|[^\\\\()])+)\\))([+*?])?'
].join('|'), 'g')

/**
 * Parse a string for the raw tokens.
 *
 * @param  {string}  str
 * @param  {Object=} options
 * @return {!Array}
 */
function parse(str, options) {
    var tokens = []
    var key = 0
    var index = 0
    var path = ''
    var defaultDelimiter = (options && options.delimiter) || DEFAULT_DELIMITER
    var delimiters = (options && options.delimiters) || DEFAULT_DELIMITERS
    var pathEscaped = false
    var res

    while ((res = PATH_REGEXP.exec(str)) !== null) {
        var m = res[0]
        var escaped = res[1]
        var offset = res.index
        path += str.slice(index, offset)
        index = offset + m.length

        // Ignore already escaped sequences.
        if (escaped) {
            path += escaped[1]
            pathEscaped = true
            continue
        }

        var prev = ''
        var next = str[index]
        var name = res[2]
        var capture = res[3]
        var group = res[4]
        var modifier = res[5]

        if (!pathEscaped && path.length) {
            var k = path.length - 1

            if (delimiters.indexOf(path[k]) > -1) {
                prev = path[k]
                path = path.slice(0, k)
            }
        }

        // Push the current path onto the tokens.
        if (path) {
            tokens.push(path)
            path = ''
            pathEscaped = false
        }

        var partial = prev !== '' && next !== undefined && next !== prev
        var repeat = modifier === '+' || modifier === '*'
        var optional = modifier === '?' || modifier === '*'
        var delimiter = prev || defaultDelimiter
        var pattern = capture || group

        tokens.push({
            name: name || key++,
            prefix: prev,
            delimiter: delimiter,
            optional: optional,
            repeat: repeat,
            partial: partial,
            pattern: pattern ? escapeGroup(pattern) : '[^' + escapeString(delimiter) + ']+?'
        })
    }

    // Push any remaining characters.
    if (path || index < str.length) {
        tokens.push(path + str.substr(index))
    }

    return tokens
}

/**
 * Compile a string to a template function for the path.
 *
 * @param  {string}             str
 * @param  {Object=}            options
 * @return {!function(Object=, Object=)}
 */
function compile(str, options) {
    return tokensToFunction(parse(str, options))
}

/**
 * Expose a method for transforming tokens into the path function.
 */
function tokensToFunction(tokens) {
    // Compile all the tokens into regexps.
    var matches = new Array(tokens.length)

    // Compile all the patterns before compilation.
    for (var i = 0; i < tokens.length; i++) {
        if (typeof tokens[i] === 'object') {
            matches[i] = new RegExp('^(?:' + tokens[i].pattern + ')$')
        }
    }

    return function(data, options) {
        var path = ''
        var encode = (options && options.encode) || encodeURIComponent

        for (var i = 0; i < tokens.length; i++) {
            var token = tokens[i]

            if (typeof token === 'string') {
                path += token
                continue
            }

            var value = data ? data[token.name] : undefined
            var segment

            if (Array.isArray(value)) {
                if (!token.repeat) {
                    throw new TypeError('Expected "' + token.name + '" to not repeat, but got array')
                }

                if (value.length === 0) {
                    if (token.optional) continue

                    throw new TypeError('Expected "' + token.name + '" to not be empty')
                }

                for (var j = 0; j < value.length; j++) {
                    segment = encode(value[j], token)

                    if (!matches[i].test(segment)) {
                        throw new TypeError('Expected all "' + token.name + '" to match "' + token.pattern + '"')
                    }

                    path += (j === 0 ? token.prefix : token.delimiter) + segment
                }

                continue
            }

            if (typeof value === 'string' || typeof value === 'number' || typeof value === 'boolean') {
                segment = encode(String(value), token)

                if (!matches[i].test(segment)) {
                    throw new TypeError('Expected "' + token.name + '" to match "' + token.pattern + '", but got "' + segment + '"')
                }

                path += token.prefix + segment
                continue
            }

            if (token.optional) {
                // Prepend partial segment prefixes.
                if (token.partial) path += token.prefix

                continue
            }

            throw new TypeError('Expected "' + token.name + '" to be ' + (token.repeat ? 'an array' : 'a string'))
        }

        return path
    }
}

/**
 * Escape a regular expression string.
 *
 * @param  {string} str
 * @return {string}
 */
function escapeString(str) {
    return str.replace(/([.+*?=^!:${}()[\]|/\\])/g, '\\$1')
}

/**
 * Escape the capturing group by escaping special characters and meaning.
 *
 * @param  {string} group
 * @return {string}
 */
function escapeGroup(group) {
    return group.replace(/([=!:$/()])/g, '\\$1')
}

/**
 * Get the flags for a regexp from the options.
 *
 * @param  {Object} options
 * @return {string}
 */
function flags(options) {
    return options && options.sensitive ? '' : 'i'
}

/**
 * Pull out keys from a regexp.
 *
 * @param  {!RegExp} path
 * @param  {Array=}  keys
 * @return {!RegExp}
 */
function regexpToRegexp(path, keys) {
    if (!keys) return path

    // Use a negative lookahead to match only capturing groups.
    var groups = path.source.match(/\((?!\?)/g)

    if (groups) {
        for (var i = 0; i < groups.length; i++) {
            keys.push({
                name: i,
                prefix: null,
                delimiter: null,
                optional: false,
                repeat: false,
                partial: false,
                pattern: null
            })
        }
    }

    return path
}

/**
 * Transform an array into a regexp.
 *
 * @param  {!Array}  path
 * @param  {Array=}  keys
 * @param  {Object=} options
 * @return {!RegExp}
 */
function arrayToRegexp(path, keys, options) {
    var parts = []

    for (var i = 0; i < path.length; i++) {
        parts.push(pathToRegexp(path[i], keys, options).source)
    }

    return new RegExp('(?:' + parts.join('|') + ')', flags(options))
}

/**
 * Create a path regexp from string input.
 *
 * @param  {string}  path
 * @param  {Array=}  keys
 * @param  {Object=} options
 * @return {!RegExp}
 */
function stringToRegexp(path, keys, options) {
    return tokensToRegExp(parse(path, options), keys, options)
}

/**
 * Expose a function for taking tokens and returning a RegExp.
 *
 * @param  {!Array}  tokens
 * @param  {Array=}  keys
 * @param  {Object=} options
 * @return {!RegExp}
 */
function tokensToRegExp(tokens, keys, options) {
    options = options || {}

    var strict = options.strict
    var start = options.start !== false
    var end = options.end !== false
    var delimiter = escapeString(options.delimiter || DEFAULT_DELIMITER)
    var delimiters = options.delimiters || DEFAULT_DELIMITERS
    var endsWith = [].concat(options.endsWith || []).map(escapeString).concat('$').join('|')
    var route = start ? '^' : ''
    var isEndDelimited = tokens.length === 0

    // Iterate over the tokens and create our regexp string.
    for (var i = 0; i < tokens.length; i++) {
        var token = tokens[i]

        if (typeof token === 'string') {
            route += escapeString(token)
            isEndDelimited = i === tokens.length - 1 && delimiters.indexOf(token[token.length - 1]) > -1
        } else {
            var capture = token.repeat ?
                '(?:' + token.pattern + ')(?:' + escapeString(token.delimiter) + '(?:' + token.pattern + '))*' :
                token.pattern

            if (keys) keys.push(token)

            if (token.optional) {
                if (token.partial) {
                    route += escapeString(token.prefix) + '(' + capture + ')?'
                } else {
                    route += '(?:' + escapeString(token.prefix) + '(' + capture + '))?'
                }
            } else {
                route += escapeString(token.prefix) + '(' + capture + ')'
            }
        }
    }

    if (end) {
        if (!strict) route += '(?:' + delimiter + ')?'

        route += endsWith === '$' ? '$' : '(?=' + endsWith + ')'
    } else {
        if (!strict) route += '(?:' + delimiter + '(?=' + endsWith + '))?'
        if (!isEndDelimited) route += '(?=' + delimiter + '|' + endsWith + ')'
    }

    return new RegExp(route, flags(options))
}

/**
 * Normalize the given path string, returning a regular expression.
 *
 * An empty array can be passed in for the keys, which will hold the
 * placeholder key descriptions. For example, using `/user/:id`, `keys` will
 * contain `[{ name: 'id', delimiter: '/', optional: false, repeat: false }]`.
 *
 * @param  {(string|RegExp|Array)} path
 * @param  {Array=}                keys
 * @param  {Object=}               options
 * @return {!RegExp}
 */
function pathToRegexp(path, keys, options) {
    if (path instanceof RegExp) {
        return regexpToRegexp(path, keys)
    }

    if (Array.isArray(path)) {
        return arrayToRegexp( /** @type {!Array} */ (path), keys, options)
    }

    return stringToRegexp( /** @type {string} */ (path), keys, options)
}


/**
 * Expose `pathToRegexp`.
 */
/*
module.exports = pathToRegexp
module.exports.parse = parse
module.exports.compile = compile
module.exports.tokensToFunction = tokensToFunction
module.exports.tokensToRegExp = tokensToRegExp
*/